BACKGROUND: Fibromyalgia is a chronic pain disorder characterized by widespread pain, multiple tender points, abnormal pain processing, sleep disturbances, fatigue, and often psychological distress. Individuals are often afflicted with fibromyalgia symptoms for years. For those with severe symptoms, fibromyalgia can be extremely debilitating and interfere with basic daily activities. Although numerous treatments are available for the management of fibromyalgia and some have showed initial promise, no treatment has demonstrated convincing effectiveness. Thus, management is difficult for clinicians. Fibromyalgia is common; affecting an estimated 10 million Americans--approximately 3%-5% of the general population. Perhaps because fibromyalgia affects more women than men, little is known about fibromyalgia in men or veterans. Fibromyalgia was diagnosed twice as frequently in Gulf War Veterans compared to non-Gulf Veterans. The prevalence in Iraq and Afghanistan War Veterans has not yet been reported. If the 2010 American College of Rheumatology (ACR) diagnostic criteria is applied, the prevalence of fibromyalgia in men rises significantly. Medications are often the first line of therapy for fibromyalgia, but are frequently associated with adverse effects and show modest treatment benefits in clinical trials and practice. Aerobic exercise programs have proven benefit, but adherence to exercise is difficult to maintain. While the literature supports psychological treatments such as cognitive behavioral therapy (CBT) for fibromyalgia, access to therapists with fibromyalgia expertise is limited. Yoga has shown initial promise for relief of fibromyalgia symptoms. However, relatively few yoga studies for fibromyalgia exist and have involved small sample sizes. With these challenges and limitations in mind, research to develop and compare different treatments for fibromyalgia, especially in veterans, is urgently needed. OBJECTIVE: The Pain Outcomes comparing Yoga versus Structured Exercise (POYSE) Trial is a 2-arm parallel group, randomized clinical trial to compare the effectiveness of a yoga-based intervention (YOGA) with that of a structured exercise program (SEP). The study aims are: 1) to compare the interventions' (YOGA vs. SEP) effects on overall fibromyalgia severity at 1 month (early response), 3 months (immediate post-intervention) and at 6 and 9 months (sustained effects); 2) to compare the interventions' effects on specific fibromyalgia symptoms (pain, sleep, and fatigue), functional impairment, and related outcomes (quality of life, psychological symptoms); and 3) to compare the cost-effectiveness of the interventions. METHODS: Our study sample will include 306 veterans with fibromyalgia. Patients will be randomized to one of two treatment arms. The YOGA arm will involve a standardized 12-week, yoga-based intervention. The yoga intervention will consist of three treatment components: 1) in-person group yoga taught by a certified yoga therapist; 2) a relaxation audio recording for home-use; and 3) a DVD recording to reinforce concepts taught during in-person yoga sessions. Patients randomized to the structured exercise program (SEP) arm will participate in a 12-week exercise program delivered in a group/class format and supervised by a fitness instructor. In addition, SEP patients will receive a DVD (for home use) describing the benefits of aerobic exercise for fibromyalgia, a one-on-one consultation session with the fitness instructor, an individualized exercise prescription, and supervised exercise sessions for 12 weeks.